This invention relates to devices for pumping coolants and more particularly to a device for pumping fluids or gasses under pressure through a laser cavity.
High powered lasers typically have powerful flash lamps which become hot after extended use. To alleviate this heating problem, lasers have a conduit through which a fluid or a pressurized gas is pumped to a heat exchanger where the coolant is cooled before being pumped back through the laser.
The present invention is for a laser coolant pump having an armature and a plurality of permanent magnets on a rotor shaft. Current flows through the armature setting up a magnetic field to turn the rotor. The rotor shaft has an impeller mounted thereto which turns to push the coolant through the pump, the heat exchanger and the laser. Bearings are mounted in the pump housing to support the rotor shaft while allowing it to rotate.
As the rotor rotates, friction causes a heat buildup between the rotor and the bearings. When current is passed through the stator, the stator also becomes hot and must be cooled. One way to cool the stator and bearing is to pass coolant or lasing material through the pump. However, the coolant may be at high temperatures when passing through the pump. As the coolant passes through the pump at these high temperatures, the material along the walls of the pump and the bearing may corrode and contaminate the coolant. When a contaminated coolant enters the laser cavity, the efficiency of the laser is reduced.
Another drawback to prior laser pumps is that the electrical motor armature must be placed adjacent the stator. This positioning is critical so that when current is passed through the stator, the armature magnetically communicates with the stator to cause it to rotate. However this placement requires that permanent magnets be placed adjacent the stator. Consequently when the coolant passes through the pump motor, it contacts the magnets which can result in contamination of the coolant by the magnets.
Many existing magnetically coupled pumps use a shaft with an impeller which encapsulates a magnet. These pumps include a heavy cantilevered drive magnet assembly with a high mass overhang moment. Consequently, the rotor can experience high moment loads under vibration. High moment loads can reduce the reliability of the pump.
Laser pumps with shafts typically include sleeve and shaft bearings. These bearings permit rotation of the shaft. However, with extended pump usage, those bearings wear out and require replacement.